Re: OT: amp - long cable - speaker = hum/noise?

[kkissinger@kevinkissinger.com]

> For me this doesn't make much sense, since I think the noise is being
> produced by the low quality of the sources
> (cd+mic+amp).  Maybe the proximity to some inductive sources...
> Perhaps good cables will help.
>

The DI boxes are for input signals, that is line, instrument, or mic  
level.  They are not suitable for power signals such as the output of  
an amp.

For starters, if the amp has a headphone jack have your friend listen  
through the headphones.  Is the hum present in the headphones?  Also,  
have him disconnect the speakers.  Is the hum still in the headphones?  
  If the hum is still present in the headphones, then the speaker  
cables are not the source of the hum.

Next, while listening through the headphones (at a relatively low  
level), unplug each input device one by one until the hum stops.  That  
is, try to identify the source of the hum.

If the amp does not have a headphone jack, then monitor through the  
speakers -- just turn the volume down so you don't put a loud pop  
through them -- and unplug your input devices one by one.

If with everything unplugged, you still get the hum, then your amp may  
have poor sheilding or a poorly designed power supply.  If you can,  
try substituting a different amp.

Your mic cable could be picking up hum... try re-routing it... it may  
be in the vicinity of a power cord or conduit.   Make sure that no  
light-dimmers are in use -- if they are you can usually get rid of the  
hum by turning the lights up all the way or just turning them off.   
Floursecent lights can also be a source of hum, too.  If you can, run  
a balanced mike cable -- unbalanced is always a battle against hum and  
noise.

Try different patch cords... or switch them around and see if the hum  
moves with the patch cords.  Again, bad shielding could be a problem.

OK, hope that this gives you a few things to look at.

Good luck!

-- Kevin